Technical Field
The present invention generally relates to display circuits, and more particularly to a pixel circuit having a pixel current control resistor and a capacitor/diode stage.
Description of the Related Art
Currently, low-temperature poly-silicon (LTPS) is a dominant thin-film transistor (TFT) technology employed in display backplanes of portable and handheld electronic devices (and almost exclusively for cell phones), due to higher performance which permits relatively lower power consumption and also scalability to lower dimensions needed for high display resolutions. However, LTPS is significantly more expensive than amorphous Si (a-Si or a-Si:H) and also requires process temperatures (e.g., 400-600° C.) which are too high for low-cost glass or plastic substrates. While LTPS can be prepared essentially at room-temperature, given short laser pulses (˜10-50 ns) used for crystallization and the rapid dissipation of the locally generated heat, the thin film transistor (TFT) fabrication process still needs high temperatures to ensure sufficient TFT performance and gate dielectric reliability.
In addition, while LTPS TFTs are more stable than a-Si:H TFTs, they are still less stable than Si VLSI devices (particularly n-channel devices which suffer from floating body/kink effects in addition to gate dielectric reliability issues). The device-to-device variation of threshold voltage requires circuit compensation techniques that reduce the display resolution due to the additional LTPS TFTs used in the pixel.